Compressor for air or other gaseous fluid



March 9, 1954 H. R RICARDO COMPRESSOR FOR AIR on o'rm GASEOUS FLUID 4Sheets-Sheet 1 Filed Aug. 4, 1952 Inventor Jim Attorney;

March 9, 1954 H. R. RICARDO 2,671,606

COMPRESSOR FOR AIR OR OTHER GASEOUS FLUID Filed Aug. 4, 1952 4Sheets-Sheet 2 Altomys March 9, 1954 O H. R. RICARDO COMPRESSOR FOR AIROR OTHER GASEOUS FLUID 4 Sheets-Sheet 3 Filed Aug. 4, 1952 Inventor ByWM 06/ M u/nfi Attorneys March 1954 H. R. RlCARDO 2,671,606

COMPRESSOR FOR AIR OR OTHER GASEOUS FLUID Filed Aug. 4, 1952 4Sheets-Sheet 4 Patented Mar. 9, 1954 A 2,671,606 COMPRESSOR FOB AIR OROTHER GASEOUS FLUID Harry Ralph Ricardo, London, England, assignor toRicardo & Co. Engineers (1927) Limited,

London, England, a company of Great Britain Application August 4, 1952,Serial No. 302,473

Claims priority, application Great Britain August a, 195i 9 Claims. 1This invention relates to compressors of th reciprocating type for airor other'gaseous fluid and of the general kind in which the admission offluid to and delivery of fluid from the cylinder or each cylinder iscontrolled by a mechanically operated admission and delivery valve.

The invention is particularly, but not exclusively, applicable tocompressors for gaseous fluid (hereinafter for convenience called aircompressors) of the type comprising a series of working cylinders, whichmay be single or double acting, lying around the axis of a driving shaftwith their axes extending axially, that is to say in a directionapproximately parallel to the axis of the driving shaft, a piston withineach cylinder connected to the driving shaft through swashplate orequivalent mechanism for converting rotary into reciprocating motion,and thus causing reciprocation of the pistons, and a rotary valvearranged in a cylindrical housing coaxially with the driving shaft andcontrolling combined admission and delivery ports communicating with theworking chambers of the cylinders.

In this type of compressor as at present made the ports in the valvesand in the cylindrical housing in which it lies are of rectangular shapeso that the timing of the opening of both the admission and deliveryports is determined by the circumferential lengths of the ports in thevalve and housing. Thus within a wide range a degree of internalcompression in each working chamber before its associated delivery portopens can be provided by making the ports of appropriate circumferentiallength, since by delaying the opening of each delivery port thecompression in the working chamber before the port opens can beincreased as desired.

When it is desired to operate an air compressor of the general kindreferred to over a wide range of delivery pressures, it is mostdesirable. for the sake of efllciency, to be able to vary the degree ofcompression which occurs in each working chamber before its associateddelivery port opens, so that the port shall open at approximately themoment when the pressure in the working chamber has reached the deliverypressure. Moreover. with rises in the delivery pressure there arecorresponding rises in the pressure in the, clearance space representingthe working chamber volume at the end of each delivery stroke, and forefliciency the compressed air in such clearance space should bere-expanded on the subsequent suction stroke down to atmosphericpressure before the associated admisoion port opens.

(C11. wit -186) The object of the prent invention is to providecompressors of the general kind referred to with an improved form ofcontrol'valve appa- 1 ratus which will tend to allow for these factors.

In a compressor of the reciprocating type for air or other gaseous fluidaccording to the present invention having an admission and deliveryvalve comprising a cylindrical valve member and housing mounted torotate relatively to one an other so as to open and close admission anddelivery ports formed in their co-operating circumferential walls, thevalve member and its housing are capable of axial movement relatively toone another and have the ports in their walls so formed that such axialmovement varies the points of opening of the delivery ports. andpreferably also of the admission ports without substantially changingtheir points of closing, and means are provided whereby the relativeaxial position of the valve member and its housing is determined by andvaried automatically with variations in the relationship between theadmission pressure and the delivery pressure.

In a preferred arrangement the cylindrical valve member is formed andarranged so that the admission and delivery pressures act respectivelyon its two ends while one or more springs act on the valve member in thesame direction as the admission pressure, so that with changesintherelationship between the admission pressure and the deliverypressure the valve moves axially automatically against or under theaction of the spring to efiect the required changes in the points ofopening of the ports. In such an arrangement one end of the housingconveniently communicates with the admission passage and the other endwith a delivery passage, while the admission and delivery passages orchambers in the valve member extend from the admission and deliveryports in its circumferential wall respectively through its two ends.Thus a simple arrangement is provided in which the two ends of the valvemember are automatically subject to the desired pressures.

The form employed for the ports to achieve the desired variations in thepoints .of opening thereof when relative axial movement occurs betweenthe valve member and its housing may vary, but preferably the edges ofthe ports in the valve member and housing which pass over one another toopen each port are similarly inclined to lines parallel to the axis ofrotation, whereas the edges of the ports which pass over one another toclose the ports are substantially parallel to such lines. Thus thedesired rapid by way of example in the accompanying drawings, in which:

Figure 1 is a sectional side elevation of the compressor, the sectionbeing taken in a plane containing the axis of the main shaft and theaxis of one pair of cylinders,

Figure 2 is a cross section on the line 2-2 of Figure 1,

Figure 3 is a cross section on the line 3-3 of Figure 1, I

Figure 4 is a cross section taken partly in the general plane of thewobble plate of the compressor and partly in a plane normal to the axisof the main shaft,

Figure 5 is an enlarged cross section showing the construction of one ofthe valves and its associated parts,- the cross section being in a planecontaining the axis of the valve, and

Figure 6 is a development view showing the form and arrangement of-theports in the valve and its housing.

In the construction shown in the drawings the compressor comprises apair of similar cylinder blocks A and A formed for example of castaluminium alloy and each comprising seven cylinders A evenly spacedaround a cylindrical valve housing A formed in the cylinder block withits axis parallel to the axes of the cylinders and having a boresomewhat larger than the bore of each cylinder and a lengthapproximately equal to that of each cylinder.

The two cylinder blocks A and A are secured to opposite ends of anintermediate housing B and each cylinder block has secured to its outerend an annular end plate C which closes the outer ends of the cylindersA and through the central aperture of which a short extension A of thevalve housing A projects. Secured to the outer face of each of the endplates C is a box section casting D, also conveniently of aluminiumalloy, which contains a discharge passage D into the inner end of whichthe adjacent and of the valve housing A .A opens as shown, thisdischarge passage having a lateral exit opening D Secured to the innerend of each cylinder block A and A so as to lie between it and theintermediate housing B is a plate having a central aperture thereinsurrounded by a series of seven circumferentially displaced apertures Eeach of which is concentric with one of the cylinders A. Secured to eachplate E so as to project through the apertures E are tubular members Feach connected by a circumferential flange to the plate and having amushroom-like head F which makes a fluid seal with the bore of thecylinder into which it projects so as to form in eflect an ixmercylinder head.

Disposed for reciprocation within each cylinder A is a piston G eachpiston G in a cylinder A in the cylinder block A being connected to oneend of a piston rod member G the other end 4 of which is connected tothe piston G in the coaxial cylinder in the block A Each piston rodmember G passes through the tubular members F associated with the innerends of the cylinders in which its pistons operate and, as will b seen,each of these tubular members is of substantial length and has parts F,F at its ends with which the piston rod member makes a close clearancesliding fit while its central part freely surrounds the piston rodmember to provide an annular chamber F to which lubricant-laden air hasaccess through passages F As will be apparent the form of the part ofeach of the mushroom like heads F of the members F which a pistonclosely approaches at the appropriate end of its stroke is such as toleave only a very small dead space-between it and the adjacent face ofthe piston.

Each of the piston rod members G is formed at the centre of its lengthwith a cylindrical housing G in which is mounted to rock a cylindricalcoupling member G six of which coupling members are identified by thereference, letter G while the seventh is of slightly differentdimensions from the others and is identified by the reference letter GEach coupling member G and G has a transverse bore G therein in which ismounted to rotate and reciprocate a pin H projecting radially from awobble plate H supported on bearings H on a member H rigidly mounted ona main shaft H and representing in efiect a so-called Z crank on thatshaft by which the wobble plate has the appropriate motion imparted toit.

As will be apparent from Figure 4, each of the coupling members G isarranged so that it is free to slide axially to a limited extent withinits housing G so as to allow for limited circumferential movement ofeach of the associated pins H relatively to its piston rod member. Inthe case of the one coupling member G however, the associated housing Ghas end caps G secured to and closing its ends and serving to preventaxial movement of the coupling member G therein. The connection thusprovided between the piston rod member and the wobble plate andincluding the coupling member G thus serves to restrain the wobble platefrom circumferential movement at the point of connection. Since thisrestraint imposes on the associated piston rod member G a certainlateral stress, the associated piston rod member is of somewhat largerdiameter than the other piston rods as shown at G in Figure 2.

Each end of the valve housing A communicates with the adjacent end ofeach of the cylinders A through a combined suction and discharge port J,the part of each of the head members F which lies adjacent to such aport being cut away as indicated at F to facilitate the flow of gasthrough the port when the piston G closely approaches the member FMounted for rotation in each of the valve housings A is a rotary valvemember K having formed therein a discharge chamber K opening through theouter end of the valve as indicated at K, and a suction chamber K whichopens through the inner end of the valve housing into a suction chamberor passage L. The discharge chamber K communicates with two dischargeports K K in the wall of the valve, these ports lying at diametricallyopposite sides of the valve and respectively in the planes of thecombined inlet and discharge ports at the ends or the associated aevneoecylinders. Similarly the suction chamber K communicates with two suctionports K K also disposed at diametrically opposite sides of the valve andlying respectively in the planes of the combined inlet and dischargeports J at the ends of the associated cylinders. As will be clear, moreespecially from Figure 5, the discharge chamber K passes in effectthrough the centre of the suction chamber K so as to provide for therequired communication of each of these chambers with the appropriateports situated towards opposite ends of the valve.

Each of the valves K is mounted upon the main H and coupled thereto by akey orsplines in a manner permitting it to move axially but not torotate thereon, and a pair of springs M, is associated with each valveand acts at one end on the valve and at its other end on a thrust memberW on the shaft H so as to tend to move the valve always towards theassociated discharge passage D The main shaft H is supported in bearingsN, N respectively in the castings D and the plates E, each of thebearings N also constituting a stop to limit the travel of the adjacentvalve K under the action of its springs M, and balancing members N aremounted on the ends of the main shaft to provide a couple duringoperation in opposition to that arising due to the motion of the wobbleplate and pistons. One of these balancing members may also constitutepart or a driving connection by which the main shaft is driven, asindicated at N.

The connecting rod members G have such a close clearance fit in thetubular guide members F at the points F and F that they support andlocate the pistons G within their cylinders A in such manner that thepistons tend not to ake contact with the cylinders and are thus enabledto operate substantially without lubrication. The pistons therefore,have no piston rings or equivalent sealing members but are preferablyeach provided with a series of closely spaced circumferential grooves asshown clearly in Figure constituting in effect a labyrinth packing.

If desired, each valve member K may also be provided with a series ofclosely spaced circumierential grooves in its circumferentially completeareas as indicated in Figure 5 and in any case each valve is preferablysupported upon the main shaft in such manner that it can operatesubstantially without lubrication between its circumferential surfaceand the wall of the valve housing A It will be apparent from the abovedescription that the pressure in each of the delivery passages D acts onthe end of the associated valve K remote from the springs M and that, ifthe force applied by the springs be appropriately determined in relationto the range of delivery pressures at which the compressor is tooperate, each valve K will, over the higher part at least of the rangeof delivery pressures, move axially against the action of its springs Mwith increases in the delivery pressure. so that its axial position atany moment will in fact be determined by the delivery pressure.

Each of the ports J, K K K and K has a leading edge, that is to say, theedge at which during operation the port first begins to open, which isinclined to lines parallel to the afi of the valve as shown in Figure 6,in which the ports J are shown in full line and the ports K K. K and K"are shown in chain line and, for

6 illustration purposes, in two alternative axial positions, that is tosay in the positions relatively to the ports J which they occupyrespectively when the valve K is in the limiting position shown inFigure 5 and when it is in its other limiting position in which thesprings M are compressed to the full extent permitted by the limitedaxial movement allowed to the valve K.

It will be apparent from Figure 6 that when the valve K occupies theposition shown in Figure 5, that is to say the position it will occupyover the lower range of delivery pressures, the ports K K K and K thenbeing in the position indicated by the reference letters K K K K inFigure 6, each of the ports J will come into communication with each ofthe ports K K K and K" somewhat sooner in each cycle than will be thecase when the valve K is moved to the right in Figure 3 against theaction of its springs M due to the delivery pressure exceeding apredetermined value and appreciably sooner than will be the case whenthe valve K is moved to the limit of its travel against the action ofthe springs M due to the delivery pressure exceeding some predeterminedmaximum.

Thus, over the higher range of delivery pres sures at least, eachdelivery port K K will open later when the delivery pressures are higherthan when they are lower and the arrangement is preferably such that thepoint at which each of these ports comes into communication with each ofthe ports J will always be approximately that at which the deliverypressure in the cylinder from which the port J opens is approximatelyequal to the pressure in the discharge passage D It will be apparentthat the suction ports will also open somewhat later when the deliverypressure is high than when it is low.

What I claim as my invention and desire to secure by Letters Batent is:

1. A gas compressor of the reciprocating type including at least oneworking cylinder having a combined admission and delivery port, aworking piston arranged for reciprocation within the cylinder, means forimparting reciprocation to said piston, an internally cylindrical valvehousing through the wall of which the combined admission and deliveryport opens, admission and delivery passages communicating with thehousing, a cylindrical valve member mounted within the housing forrotation relatively thereto and having admission and delivery ports inits circumferential wall cooperating with the combined admission anddelivery port for the control of the flow of. working fluid to and fromthe working cylinder, the valve member and its housing being capable ofaxial movement relatively to one another and having the edges of theports in their circumferential walls so formed that such axial movementvaries the point of opening of both the admission and delivery portswithout substantially changing their points of closing, and pressureresponsive and resilient means which vary automatically the relativeaxial position of the valve member and its housing in response tovariations in the relationship between the pressure respectively in theadmission and delivery passages so as to vary the points of opening ofthe admission and delivery ports.

2. A gas compressor of the reciprocating type comprising at least oneworking cylinder: having at least one combined admission and deliveryport, a piston mounted to reciprocate within the working cylinder, meansfor imparting reciprocation to said piston, an internally cylindricalvalve housing through the circumferential wall of which the combinedadmission and delivery axial movement varies the point of opening ofboth the admission and delivery ports without substantially changingtheir points of closing, and pressure responsive and resilient means forautomatically varying the relative axial position of the valve memberand its housing in response to variations in the relationship betweenthe pressures respectively in the admission and delivery passages so asto vary the points of opening of the admission and delivery ports.

3. A gas compressor of the reciprocating type as claimed in claim 2, inwhich the-admission and delivery chambers in the valve member openthrough its ends, the admission and delivery passages rigid with thhousing communicate with the ends of the housing, and the means forautomatically varying the relative axial positions of the valve memberand its housing with variations in the relationship between thepressures respectively in the admission and delivery passages include aspring acting on the valv member in a direction tending to move itaxially towards the delivery passage, this spring being thereforepartially or wholly counterbalanced by the pressure in the deliverypassage.

4. A gas compressor of the reciprocating type comprising a plurality ofparallel working cylinders arranged symmetrically about an axis, acylindrical valve housing coaxial with that axis and around which theworking cylinders lie, each working cylinder having at least onecombined admission and delivery port opening through the circumferentialwall of the cylindrical valve housing, working pistons mounted forreciprocation within the working cylinders, means for impartingreciprocation to the working pistons including a main driving shaftcoaxial with the said axis, admission and delivery passages rigid withthe working cylinders and valve housing and communicating directlyrespectively with the two ends of th valve housing, a cylindrical valvemember mounted for rotation and limited axial movement within the valvehousing and containing admission and delivery chambers which communicatethrough the ends of the cylindrical valve member respectively with theadmission and delivery passages and communicate with admission anddelivery ports formed in the circumferential wall of the valve memberfor cooperation with the combined admission and delivery ports of thecylinders, a driving connection between the valve member and the maindriving shaft, the edges of the ports in the valve member and housingbeing so formed that axial movement of the valve member within thehousing varies the points of opening of both the admission and deliveryports without substantially changing their points of closing, andpressure responsive and resilient means for varying automatically theaxial position of the valve member within its housing in response tovariations in the relationship between the pressures respectively in theadmission and delivery passages so as to vary the points of opening ofthe admission and delivery ports.

5. A gas compressor of the reciprocating type as claimed in claim 4, inwhich the means for automatically varying the axial position of thevalve member relatively to its housing include at least one springacting on the valve member in a direction tending to move it alwaystowards the delivery passage.

6. A gas compressor of the reciprocating type as claimed in claim 5, inwhich each of the working pistons is double-acting and the valve memberincludes admission and delivery chambers communicating respectively withthe two ends of the valve member and each communicating with a pair ofdiametrically opposite ports in the circumferentiaI wall of the valvemember coopcrating respectively with the combined admis sion anddelivery ports at the opposite ends of the working cylinders.

7. A gas compressor of the reciprocating type as claimed in claim 4, inwhich the means for automatically moving th valve member axiallyrelatively to its housing includes at least one spring tending always tomove the valve member axially towards the delivery passage.

8. A gas compressor of the reciprocating type as claimed in claim 5, inwhich the edges of the ports in the valve member and in the valvehousing which pass over one another to open each port are similarlyinclined to lines parallel to the axis of rotation of the valve member,whereas the edges of the ports which pass over one another to close theports are substantially parallel to such lines.

9. A gas compressor of th reciprocating type as claimed in claim 4, inwhich the edges of the ports in the valve member and in the valvehousing which pass over one another to open each port are similarlyinclined to lines parallel to the axis of rotation of the valve member,whereas the edges of the ports which pass over one another to close theports are substantially parallel to such lines.

HARRY RALPH RICARDO.

References Cited in the file of this patent FOREIGN PATENTS Number

